The Ligand Assay Core Laboratory of the DRTC has been in operation since this grant was first funded in 1977. The name of this Core has been changed from Radioimmunoassay and Clinical Studies to Ligand Assay Core Laboratory to reflect movement away from radioimmunoassay to non-radioactive methods for assaying insulin and other hormones. At the last competitive renewal, this Core was judged to have outstanding merit. This Core helps independently funded investigators with an interest in diabetes mellitus and other metabolic disorders by assaying insulin, C-peptide, proinsulin and other hormones. In the previous funding period, Dr. Kenneth Polonsky was Director of this Core. In the current application, Dr. Samuel Refetoff is Director of the Ligand Assay Core Laboratory with Dr. David Ehrrnann serving as Co-Director. Dr. Refetoff is currently Director of the University of Chicago Hospitals Clinical Endocrinology Laboratory and he is an excellent person to serve as Director of this Core Laboratory. Dr. Ehrmann is a major user of the Core Laboratory and is thus an ideal choice for Co-Director. Dr Neal Scherberg will be the Technical Director and is highly qualified for this position.A detailed progress report outlining the growth and effectiveness of the Ligand Assay Core Laboratory follows.